An electric source system that is provided with: an electricity storage apparatus such as a secondary battery and a capacitor; and an electric power converter that is configured to perform an electric power conversion with the electricity storage apparatus by changing switching state of switching element, is known. For example, a Patent Literature 1 and a Patent Literature 2 disclose an electric source that is configured to perform the electric power conversion by changing the switching state of the switching element so that an efficiency of the electric power conversion in the entire electric source system can be increased (namely, a loss of an electric power can be reduced).
Moreover, a Patent Literature 3 and Patent Literature 4 are listed as background art documents that are related to the present invention.